[dagskarlsen]

Thank you for that hint. I found one, and a diagram inside:

Converting to UK system with master socket:

Remove original line cord.
Remove any link found between terminals 3 and 4.
Connect a 2.2k resistor to terminals 3 and 4.
Connect red of the line cord to terminal 2.
Connect white of the line cord to terminal 3.
Insulate the blue and green wires of the line cord.

It will probably work without doing whats marked with blue.